GOGKLEBUR 



ALBERT A. HANSEN 

Agronomist, Office of Forage-Crop Investigations 




UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 109 



Contribution from the Bureau of Plant Industry 

( OiBce of Forage-Crop Investigations ) 
WM. A. TAYLOR, Chief 



Washington, D. C. 



July, 1920 



Washington': GOVERNMENT printinq office : 1920 



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COGKLEBUR. 



CONTENTS. 



Page. 

Distribution of cocklebur 3 

Description.'. 3 

Damage 5 



Page. 

Uses 5 

Eradication 5 



DISTRIBUTION OF COCKLEBUR. 

THE common name cocklebur is applied to about a dozen species 
growing on rich lands in practically all parts of the United 
States except in the dry Southwest and the mountain areas. All 
these species are contained in the botanical genus Xanthium. Unlike 
nearly all of our troublesome weeds, most species of cocklebm' are 
native. Other common names of cocklebur are clotbur, burweed, 
bathurst bur, sheep bur, bur thistle, buttonbur, hedgehog bur, and 
ditchbur. Cockleburs are found along roadsides, fence rows, and 
river banks, in waste places, farmyards, ditches, pastures, and fre- 
quently in cornfields. The}^ show a marked preference for moist 

places. 

DESCRIPTION. 

Cockleburs arc so common that they hardly need to be described. 
Practically ail of the dozen species of cocklebur are troublesome. 
The various species, with the exception of the spiny cocklebur 
{Xanthium spinosum), resemble each othex closely and are similar 
in habit; hence, a general description will be sufficient. The spiny 
cocklebm- differs from the remaining species by the possession of 
numerous 3-pronged yellow spines, each about an inch long, and 
•dark-green shiny leaves with conspicuous white lines and white 
do\\Tiy beneath. 

The cockleburs are all annuals, which means that they mature seeds 
in a single season and then die. They produce a stout, rank growth, 
usually from 1 to 4 feet high, although the height varies with con- 
ditions; specimens a few inches in height may frequently bear 
mature seed, especially in late fall. The outstanding characteristic 
is the possession of spiny burs (fig. 1) about three-fourths of an inch 
long, each containing two single-seeded chambers. The spines are 
hooked, while at the top of the bur may be found in most species 
two stout hooked beaks. In the common species of cocklebur the 
leaves and stems are exceedingly rough. Two kinds of flowers are 
formed, one producing pollen and the other forming seed. The 

185117°— 20 ^ 



4 Department Circular 109, U. S. Dept. of Agriculture. 

pollen-producing flowers appear on the upper branches, an arrange- 
ment which permits the pollen to fall upon the seed-forming flowers 
much in the same fashion as with corn. After pollination, the pollen- 
producing flowers wither and fall off. The root is stout and usually 




ii 



Fig. 1.— Cocklebur {Xanthium commune). '1, A single bur, showing the two hooked beaks at the 
apex; 2, a portion of the plant, showing the burs and the branches of the male flowers above the 
burs. 

unbranched, penetrating the soil frequently to a depth of a foot or 
more. 

Cockleburs are sometimes confused with burdock because of the 
resemblance of the burs, l)ut they may be easily distinguished by the 



Cocklebiir. r 

fact that the burs of cocklebur contain two seeds, while those of the 
burdock contam more than two. Also burdock bui-s do not possess 
the pair of hooked beaks usually found on the cocklebui'. 

DAMAGE. 

Aside from its general unsightluiess on the farm and the severe 
damage done to crops such as corn, cockleburs also occasionally kill 
swine and young cattle. Although fatal results are generally at- 
tributed to poisoning, there is little evidence to substantiate this 
theory. The harmful effects are largely due to the mechanical action 
of the spiny burs, which are injurious in several ways. These burs 
may (1) irritate the walls of the stomach, causmg inflammation and 
sometimes death; (2) lodge in the throat and thus choke the animal; 
or (3) clog the intestinal tract, frequently with fatal results. 

Overeating the young and succulent plants may cause bloating, 
which is similar in nature to bloating caused by succulent clover, 
corn, etc. The hairy leaves are also said to cause severe itching. 

Serious loss is occasioned by the burs beconung tangled in the wool 
of sheep and in the hair of Angora goats. The presence of the burs 
causes the heavy dockage of wool, a fact which makes cocklebur one 
of the greatest enemies of woolgrowers. 

USES. 

Lately, a method of extracting oil from cocklebur seed has been 
developed, producing a valuable oil useful for paints and varnishes 
and as human food. The resulting cake is utilized for feed and fer- 
tilizer in the same manner as cottonseed oil cake. The burs are also 
used in the manufacture of advertising novelties, a practice which 
shoidd be discouraged, since it tends to spread the pest. 

ERADICATION. 

Methods of eradicating cockleburs should aim to prevent seed pro- 
duction and to destroy the seeds already contamed in the soil. With 
any method of eradication the fact should be remembered that one of 
the two seeds contained in the bur normally sprouts durmg the first 
season, while the other germmates the following season. During wet 
seasons the two seeds may germinate together, suggesting that such 
a time is particularly favorable for eradicating the plant. 

Smce cockleburs are annuals, they must eventually disappear if the 
production of seed is not permitted, although the delayed germination 
of one seed will continue the weed for an additional year, and buried 
burs may contain seeds viable for several years. 

If cocklebur-infested land is to be planted in corn, it should be 
plowed early in the spring and then harrowed at least twice before 
planting, in order to induce the germination of cocklebur seeds and 
to destroy any cocklebur seedlings which may have developed. 



6 Department Circular 109, U. S. Dept. of Agriculture. 

The subsequent cultivation of the corn should be thorough, special 
care being exercised to remove plants of cocklebur which may grow 
in the corn hills out of reach of the cultivator. " Such stray plants 
may be removed by hand or cut with a hoe. Extra care should be 
taken to prevent cockleburs from maturing seeds after the corn is 
laid by, since the weed usually forms seed until the first severe frost. 
Two or three seasons may be required to effect complete control of the 
weed, but persistence is sure of reward. 

In grainfields cockleburs do not grow very luxuriantly until after 
the removal of the crop ; the cockleburs should then be plowed under 
before they mature seeds. In the North early fall plowing before 
the seed ripens is always good practice for controlling this weed. 

The weed may be destroyed by the use of any good shading crop, 
such as buckwheat, soy beans, or cowpeas. Clover is particularly 
useful in subduing cocklebur. Close grazing with sheep, especially 
in grain stubble, is a very useful ^practice. In heavily infested areas 
mowing and burning have been successfully practiced. Plants in 
waste places should be removed by mowing before burs are formed, 
or, better still, by hand removal following rain, when the ground is 
soft. The spud, mattock, and hoe are all useful instruments in 
eradicating cocklebur. The removal of cockleburs from waste areas 
is of special importance, because the burs from a single plant may 
spread to all parts of the farm, since they adhere readily to the 
clothing of passers-by or to the coats of animals. 

If the farm is equipped with spraying machinery it is practicable 
to destroy cockleburs entirely by spraying early in the spring with 
a solution of iron sulphate used at the rate of 2 pounds of the chemi- 
cal to a gallon of water. 



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